Mysql Workbench failing with "SSL connection error: protocol version mismatch" (even when is explicitly setting SSL: NO)

On newer versions of Mysql Workbench (at least versions 6.3.5 to 6.3.7) there is a bug preventing you to connect to your instance, even if you don't use SSL. You will have to downgrade your client to avoid this error.

Windows

Please uninstall your current version via the control panel (Control Panel\Programs\Programs and Features), download version 6.3.4 and install it. Your config files will be kept.

OSX

Just download the package and overwrite the old one. Your config files will be kept.

Just in case, you can save your connections in Mysql Workbench through the tab Tools -> config -> backup connections.

The root cause is a renewal of the certificates on the machines after your instance was started, making SSL connections impossible. If you want to use SSL, you will have to restart your instance for it to take the newer certificates into account. Please check MYSQL SSL Configuration